For starters...
I suspect Apple might view HomePod being used in a home environment where there might be multiple family members who want to engage it. Husband, wife, and a few children. And maybe even a guest.
I might want to ask the question, "What is the balance in my checking account today?" Before reporting the balance, I would hope HomePod would first ascertain my identity, and then report the balance of my (and not a family member's) checking account.
I could go on... Let me know if you need more possibilities.
Why the need for facial recognition, when voice recognition could do the same thing? But the thing with any of the IoT connected speakers on the market is that with the number of people, including young kids, carrying an iPhone or Android phone with them all the time, I just don't see the value in having yet another screened device that you would need to get up to go to in order to interact with the screen it has.
If you want to know what your balance is in your account, why not just pull your iPhone out of your pocket and check your bank's app? Or better yet, have the app set up to provide notifications first thing in the morning and you can just look at the notification to see what the balance is. That's how I currently keep track and it's super easy.
I think Apple's Home Pod is really just a re-imagining of their previous home speaker system, and is not supposed to be an alternative to your iPhone or iPad for interacting with on such a personal level.